Bioerosion in the carbonate budget of two Indo-Pacific reefs: La Réunion (Indian Ocean) and Mooréa (Pacific Ocean)

On coral reefs, products of bioerosion through the activity of micro- and macro-boring organisms and grazers are particulate and dissolved carbonate. The con-tribution to bioerosion of the major boring and grazing species was estimated on French Polynesia and the island La Réunion. The influence of bioerosion on the calcification/dissolution budget of reefal waters and on particulate calcium car-bonate fluxes was investigated. Studies on bioerosion were performed in order to assess: (a) eroding activity of grazers through the gut content analysis of echinoids and scarid parrot fish, (b) eroding activity of micro- and macroborers from ex-perimental substrates exposed for one year, and (c) role of sponges in total bioero-sion on reefal and experimental substrates. Calcification/dissolution budget was measured using the alkalinity anomaly technique, and particulate carbonate pro-duction was analysed from trapped sediments.